Yarn Feeder Device

ABSTRACT

The device comprises a sensor ( 15 ) for reading the tension of the yarn being fed to the machine and a variable-speed motor-driven yarn feed roller ( 3 ). The roller is driven by a microprocessor-controlled unit suitable for adjusting the speed of the roller as a function of the signal coming from said tension sensor. The yarn delivered by the feed roller ( 3 ) is wound through approximately 180° onto an idle pulley ( 13 ) before it is fed to the textile machine.

This invention relates to a device for feeding yarns to textilemachines, such as circular or straight knitting machines, that can beadapted either to machines in which the yarn consumption rate isconstant or to machines in which the yarn is knitted discontinuously (itis a well-known fact that said discontinuous yarn consumption inducesperiodic changes in the yarn's tension that can combine with tensionvariations due to irregularities in the yarn itself in negativelyinfluencing the quality of the resulting fabric and the continuity ofits production).

The device forming the object of this invention can also be used incertain stages of the spinning process, e.g. to feed yarn at a uniformtension to twisting or stranding machines, or the like.

This invention refers to a yarn feeder device comprising a yarn tensionsensor and a yarn feed roller around which the yarn is wound to preventany relative slipping, the roller being motorized by means of avariable-speed motor complete with a rotation sensor and governed by amicroprocessor-controlled electronic unit suitable for adjusting thespeed of the roller as a function of the signal coming from said tensionsensor.

According to this invention, the device comprises a pulley for carryingthe yarn, wherein the incoming and outgoing lengths of yarn togetherform a relatively narrow, or substantially near-zero angle (α). Thepulley is suspended from a sensitive element of the tension sensorsuitable for transmitting a signal to said feed roller motor controlunit that is proportional to the resultant of the forces exerted on thepulley by the yarn, and the control unit has a program resident in itsmemory for keeping the value of said resultant of the forces(corresponding to the yarn tension) within a pre-established range ofyarn tensions by adjusting the speed of the motor, and consequently ofthe feed roller. The yarn thus brings a force to bear on the tensionsensor that is approximately twice the actual tension of the yarn,thereby increasing the sensor's sensitivity by comparison with knownfeeder devices.

The electronic control unit of the device can also be interfaced withthe machine to which the device is attached in order to receive data(e.g. using suitable sensors) and/or instructions from the latter, andto adjust the working tension of the yarn being fed to the machineaccordingly, depending on its working program, or it can send themachine information such as the length of yarn delivered in each workingstage. The previously-mentioned tension adjustments can be made in stepsor continuously, depending on the needs of the garment being made by themachine, and they can be set by means of an operator interface connectedto the control unit of the device, such as a personal computer eitherconnected to said control unit or on board the machine itself.

In a first preferred embodiment of the invention, the pulley supportingblock comprises a U-shaped bracket housing the pulley, the studsupporting the pulley being attached to the ends of said bracket. Thesensor is of the slender cylinder-shaped type and is glued to a flat orconcave seat coinciding with the end of the rod, with its axis lyingparallel to said rod, said U-shaped bracket resting up against thesensor on the side opposite said seat on the rod.

In a second preferred embodiment, the pulley block bracket is hingedonto one free end of a tab to which a bending sensor is attached,composed for instance of one or more strain gauges.

According to the invention, the tension sensor, and consequently also astud from which the pulley carrying the yarn is suspended, can besolidly attached to the body of the feeder device, or applied to thefree end of a yarn take-up rod. This second solution is particularlysuitable when the machine served by the feeder device has adiscontinuous yarn consumption rate.

Various structural variants and possible uses of the device according tothis invention are described in the dependent claims.

The invention is better explained in the following description andattached drawings, which illustrate a non-restrictive example of theinvention in question.

In the drawings:

FIGS. 1 and 2 schematically illustrate an elevational view and a viewfrom above (along II-II of FIG. 1), respectively, of the deviceaccording to a first embodiment of the invention;

FIGS. 3 and 4 show partial views from above along III-III and IV-IV ofFIG. 1;

FIG. 5 is an enlargement of the detail V in FIG. 1;

FIG. 6 is a cross-section along VI-VI of FIG. 5;

FIG. 7 shows a side view of another form of embodiment of the deviceaccording to the invention;

FIG. 8 shows an enlargement of the detail VIII in FIG. 7; and

FIG. 9 shows a view along IX-IX of FIG. 8.

With reference to FIGS. 1 and 2, the device according to the inventionhas a plate-shaped body 1, to which a variable-speed electric motor(e.g. of the brushless, direct-current type) and a correspondingelectronic control unit (not illustrated in the drawing) are attached.On the front of the body 1 illustrated in FIG. 1, the device has arevolving roller 3 mounted co-axially on the output shaft of the motor,a plate-type yarn tensioner 5, a rod 7 swinging around an axis X-X, arod-returning spring 9, an arched blade serving as a rabbet 10 for therod 7, and a graduated segment 12 of a circle whose center lies on theaxis X-X, suitable for identifying the angular position of the rod 7.

The roller 3 has a cylindrical outer surface suitable for generating afriction with the yarn wound thereon, made of elastomer for instance, orwith a hard, rough metal surface layer. The plate-type yarn tensionercomprises a pair of plates 5A, 5B (FIG. 3) kept in contact with eachother—on their smooth, wear-proof sides—by a compression spring 5Cadjustable by means of a threaded knob 5D. The spring 9 is a tractionspring that obliges the rod 7 to turn in the direction of the arrow F1,one end of the spring being attached by means of a screw to theperiphery of the hub 7A of the rod, and the other end being fixed bymeans of another screw to the periphery of a bush 8 attached to thefront of the body 1 by means of a swivel screw 8A (FIG. 4). The tensionon the spring 9 can be adjusted by loosening the screw 8A, turning thebush 8 one way or the other, and then tightening it again in therequired position.

A block 11 is attached to the free end of the rod 7 and comprises anidle pulley 13 with an outer race 13A, and a holder for the pulleysubstantially composed of a bracket 11A bent into a U shape, with thestud 11B supporting the pulley 13 caulked onto its ends.

The block 11 is kept axially on the rod 7 with some degree of clearanceby means of a pair of elastic rings 7B inserted in corresponding grooves(not illustrated) in the rod 7, and rests against the rod 7 with apressure sensor 15 sandwiched between the two and attached to the rod,e.g. by means of glue, in a cavity 7C in said rod. The pressure sensor15 is electrically connected to the electronic control unit contained inthe body 1, by means of electric wires not illustrated in the drawing.

The above-described device can feed yarn 17 to a textile machine forprocessing, to produce a knitted fabric for instance. The yarn (comingfrom a reel that is not illustrated in the drawing) passes through theadjustable yarn tensioner 5, then winds at least one turn around theroller 3 before passing through the race 13A in the pulley 13, whichreturns it through a yarn guide 19 to deliver it to the machine forprocessing. The lengths of yarn entering and exiting from the pulley 13together form a very narrow angle α (e.g. approximately 7° in theexample in FIG. 1). Using this arrangement, the tension of the yarn isunloaded onto the sensor 15 with a resultant corresponding toapproximately twice its real value.

In working conditions, the tension of the yarn being processed makes therod 7 turn in the direction opposite the arrow F1 of FIG. 1, overcomingthe effect of the spring 9. The force exerted by the spring is adjustedby the operators, who adjust the angular position of the bush 8 so that,with the required tension on the yarn, the rod 7 is positioned at acertain angle with respect to the graduated segment 12, e.g.approximately at the midline thereof. The control unit contained in thebody 1 receives a signal from the pressure sensor 15 that isproportional to the tension on the yarn 17; it compares the signal withthe required tension previously specified in its resident memory, andthen it adjusts the speed of the motor driving the roller 3 so as tokeep the tension of the yarn 17 close to the required value. Forinstance, if the pressure recorded by the sensor 15 corresponds to atension higher than the required setting, the control unit acceleratesthe movement of the roller 3; vice versa, it makes the roller turn moreslowly if said pressure tends to diminish with respect to the pre-setvalue.

When the machine upstream calls for more yarn than is currently beingdelivered by the roller 3, the rod 7 is drawn downwards, even to thepoint where it comes up against the arched rabbet blade 10. Thismovement of the rod 7 prevents any excessively rapid increases in thetension of the yarn 17, an action that is prolonged both by the rod 7bending (thanks to its flexibility) against the rabbet 10 and by theshape of said rabbet 10.

With reference to FIGS. 7 to 9, the following is a description ofanother particularly preferred embodiment of the invention. As in thecase of FIG. 1, the device has a plate-shaped body 201, to which avariable-speed electric motor (e.g. of the brushless, direct-currenttype) and a corresponding electronic control unit (not illustrated inthe drawing) are attached. On the front of the body 201 illustrated inFIG. 7, the device has a revolving roller 203 mounted co-axially on theoutput shaft of the motor, that is on the opposite side of the plate201, a plate-type yarn tensioner 205 entirely similar to the one 5 inFIG. 1, a rod 207 swinging around an axis X-X, and a rod-returningdevice 209.

The take-up rod 207 is obliged to move clockwise (looking at FIG. 7) bya wheel 212 idly supported onto the end of a small rod 214, which is inturn hinged along an axis Y-Y to a saddle 216 sliding on a horizontalguide 217 and attachable thereto, in the preferred position, by means offixing means that are not illustrated in the drawing. A spiral spring220, working between the small rod 214 and the saddle 216, obliges saidsmall rod to move clockwise so as to rest against the take-up rod 207,making the latter turn in the same direction. Changing the position ofthe saddle 216 along the guide 217 induces a variation in the pointwhere the wheel 212 comes to rest along the rod 207, and thisconsequently enables an accurate adjustment of the return torque broughtto bear thereon. The saddle 216 also has an extension 216A, which servesas a rabbet for the rod 207, restricting its downward movement due tothe tugging of the yarn.

One end of a tab 221, in the form of a thin, narrow and elongated plate,is welded onto the free end of the rod 207; the upper side of the otherend of said tab is welded to a bush 221A for a stud enabling theswinging of a bracket 211, which carries an idle pulley 213, saidbracket and pulley being similar and serving the same purposes as thecorresponding elements 11 and 13 of FIG. 1. Two strain gauges 215 areattached to the two sides of the tab 221, which are electricallyconnected, forming a bridge, to the control unit (not illustrated) ofthe device and serving the same purpose as the sensor 15 of FIG. 1.

Normally, as it moves along, the yarn 17 (FIG. 7) fed by the deviceencounters the plate-type tensioner 205 first and then, after beingdiverted by a counter-roller 223 (which is idly hinged onto a lever 225,that is in turn hinged to the plate 201 and held by a spring 227 upagainst the roller 203), the yarn is wound through approximately 180°onto the motor-driven roller 203 and then passes onto the pulley 213,being diverted by the latter through approximately 180° and exiting fromthe device through a yarn guide 219 attached to the plate 201.

The device according to this embodiment of the invention is extremelysensitive to the feed tension of the yarn due to the sensor with the twobridging strain gauges 215, so it facilitates the passage of the yarnonto the feed roller 203, where it is wound only through 180°, and italso enables a precise and easy adjustment of the take-up rod 207returning torque by means of the adjustable saddle 216.

Clearly, the drawing only shows one example, given exclusively as apractical illustration of the invention, which may vary in form andarrangement without departing from the concept underlying saidinvention. Any use of reference numbers in the attached claims is madeexclusively to facilitate the reading of the claims with reference tothe description and shall in no way restrict the scope of protectionrepresented by the claims.

1-19. (canceled) 20: A yarn feeder device for use with textile machines,and particularly for circular or straight knitting machines, or forspinning machines, e.g. twisting or stranding machines, etc.,comprising: a yarn tension sensor; and a revolving roller, around whichthe yarn is at least partially wrapped to prevent any relative slipping,the roller being motorized by means of a variable-speed motor providedwith a rotation sensor and driven by a microprocessor-controlledelectronic unit or other equivalent device for adjusting the speed ofthe roller as a function of the signal coming from said tension sensor;wherein said device further includes a pulley carrying the yarn, inwhich the incoming and outgoing lengths of yarn together form arelatively narrow, substantially near-zero angle, the pulley beingsuspended from a sensitive element of the tension sensor so as totransmit a proportional signal to said control unit for the motor of thefeed roller that is approximately twice the tension of the yarn, thecontrol unit being provided with a program resident in its memorycapable of keeping said signal, which corresponds to the tension of theyarn, within a previously-established range of yarn tensions byadjusting the speed of the motor and consequently of the roller. 21: Thedevice as in claim 20, wherein said pulley block comprises a U-shapedbracket for housing the pulley, the stud supporting the pulley beingattached to the ends of said bracket, and wherein said sensor is of theslender cylinder-shaped type and is glued to a flat or hollow seat atthe end of the rod, with its axis lying parallel to said rod, saidU-shaped bracket resting up against the sensor on the side opposite saidseat in the rod. 22: The device as in claim 20, wherein the U-shapedbracket is held axially with respect to the rod by means of elasticrings inserted in corresponding grooves in the rod or in the stud, andarranged on opposite sides of the bracket. 23: The device as in claim21, wherein the U-shaped bracket is held axially with respect to the rodby means of elastic rings inserted in corresponding grooves in the rodor in the stud, and arranged on opposite sides of the bracket. 24: Thedevice as in claim 20, wherein said sensitive element of the sensorcomprises a tab in the shape of a thin, narrow, elongated plate on onefree end of which a bush is welded, that is engaged or hinged to apulley block comprising a bracket that carries the idle pulley, with atleast one strain gauge attached to at least one of the two sides of thetab, electrically connected to the control unit of the device and actingas the tension sensor. 25: The device as in claim 24, wherein respectivestrain gauges are attached to the upper and under-sides of the tab andsaid strain gauges are connected to form an extensometric bridge withsaid control unit. 26: The device as in claim 20, wherein said sensitiveelement for the tension sensor is fixed to the body of the device. 27:The device as in claim 20, wherein said sensitive element for thetension sensor is fixed to the free end of a yarn take-up rod. 28: Thedevice as in claim 27, wherein said rod is flexible so that, when it isdrawn down by the yarn against a rabbet that restricts its movement, therod opposes a gradually increasing resistance to the yarn to absorb thepeaks in the tension of the yarn. 29: The device as in claim 28, whereinsaid rabbet is also flexible so as to further absorb the peaks in thetension of the yarn. 30: The device as in claim 28, wherein said rabbetis in the form of an arch so as to oppose an increasing resistance asrod bends, and thus further absorb the peaks in the tension of the yarn.31: The device as in claim 20, wherein said rabbet is attached to anadjustable saddle that also carries a device suitable for exerting anadjustable return torque on the rod. 32: The device as in claim 31,wherein said device for adjusting the return torque on the take-up rodincludes a lever hinged to the saddle, whereon a spring comes to bear,the lever resting, under the influence of said spring, either directlyor by means of a wheel, against said take-up rod at a point on thelatter that depends on the position where the saddle is attached alongthe guide. 33: The device as in claim 20, wherein, depending on thesignals transmitted by the yarn tension sensor, the control unit of thedevice enables the operation of the machine to which the device isapplied to be controlled: stopping it, for instance, in the event of theyarn breaking; or slowing it down, for instance, in the event of thepassage of knots in a yarn clearer, or when the yarn runs out or breaks,in which case the tension sensor registers a lack of tension persistingbeyond a given time threshold. 34: The device as in claim 20, wherein,based on the signals transmitted by the yarn tension sensor, the controlunit of the device enables weaving parameters to be recorded, such asthe actual quantity yarn instantaneously or globally fed to the machinefor the preparation of a given quantity of fabric, the total number ofstoppages, and so on. 35: The device as in claim 1, wherein the controlunit of the device is interfaced with the machine to which the device isattached in order to receive data and/or instructions from said machineand thus adjust the working tension of the yarn being deliveredaccordingly, depending on a working program of said machine, saidadjustments being possible both in stepping or in continuous mode 36:The device as in claim 20, wherein the control unit of the device alsoincludes means for turning a waxing device on or off. 37: The device asin claim 20, wherein the control unit of the device also includes meansfor changing the turning speed of a variable-speed to suit the turningspeed of the feed roller. 38: The device as in claim 20, wherein themotor driving the roller is of the type that can be made to turn in bothdirections to allow for the use of the device to undo knitted articlesby coupling it with a reel-winding device.